| Document And Entity Information | Aug. 12, 2020 |
| Document Information [Line Items] | |
| Entity, Registrant Name | AMERICAN NATIONAL BANKSHARES INC. |
| Document, Type | 8-K |
| Document, Period End Date | Aug. 12, 2020 |
| Entity, Incorporation, State or Country Code | VA |
| Entity, File Number | 0-12820 |
| Entity, Tax Identification Number | 54-1284688 |
| Entity, Address, Address Line One | 628 Main Street |
| Entity, Address, City or Town | Danville |
| Entity, Address, State or Province | VA |
| Entity, Address, Postal Zip Code | 24541 |
| City Area Code | 434 |
| Local Phone Number | 792-5111 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | AMNB |
| Security Exchange Name | NASDAQ |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0000741516 |
